Some Atthakatha glosses:
https://www.dhammawheel.com/viewtopic.php?f=23&t=37315&sid=c6d2e0748c904cbed094b88b3bc39236
sugatanti gocare gatattā suṭṭhu gataṃ.
DN-a 3, 10. saṅgītisuttavaṇṇanā, nissaraṇiyapañcakavaṇṇanā, para. 1
AN-a 5, 4. catutthapaṇṇāsakaṃ, (20) 5. brāhmaṇavaggo, 10. nissāraṇīyasuttavaṇṇanā, para. 1
sugatanti sundaraṃ ṭhānaṃ gataṃ, sundarāya vā paṭipattiyā gataṃ.
MN-a 2, 5. brāhmaṇavaggo, 8. vāseṭṭhasuttavaṇṇanā, para. 40
sugatanti sammā paṭipannaṃ kalyāṇaputhujjanena saddhiṃ aṭṭhavidhaṃ ariyapuggalaṃ.
KN-a It, 4. catukkanipāto, 8. bahukārasuttavaṇṇanā, para. 5
sugatanti sobhanagamanattā sundaraṃ ṭhānaṃ gatattā sammā gadattā sammā ca gatattā sugataṃ bhagavantaṃ.
KN-a Thī, 6. chakkanipāto, 2. vāseṭṭhītherīgāthāvaṇṇanā, para. 22
A gloss from the Tika:
♦ Sobhanaṃ gataṃ gamanaṃ etassāti sugato. Bhagavato hi veneyyajanupasaṅkamanaṃ ekantena tesaṃ hitasukhanipphādanato sobhanaṃ, tathā lakkhaṇānubyañjana (dī. ni. 2.33; 3.198-200; ma. ni. 2.385, 386) paṭimaṇḍitarūpakāyatāyadutavilambita- khalitānukaḍḍhananippīḷanukkuṭikakuṭilākulatādidosarahitaṃ vilāsitarājahaṃsavasabhavāraṇamigarājagamanaṃ kāyagamanaṃ ñāṇagamanañca vipulanimmalakaruṇāsativīriyādiguṇavisesasahitamabhinīhārato yāva mahābodhi anavajjatāya sobhanamevāti.
♦ Atha vā sayambhuñāṇena sakalampi lokaṃ pariññābhisamayavasena parijānanto ñāṇena sammā gato avagatoti sugato. Tathā lokasamudayaṃ pahānābhisamayavasena pajahanto anuppattidhammataṃ āpādento sammā gato atītoti sugato. Lokanirodhaṃ nibbānaṃ sacchikiriyābhisamayavasena sammā gato adhigatoti sugato. Lokanirodhagāminipaṭipadaṃ bhāvanābhisamayavasena sammā gato paṭipannoti sugato. Sotāpattimaggena ye kilesā pahīnā, te kilese na puneti, na pacceti, na paccāgacchatīti sugatotiādinā nayena ayamattho vibhāvetabbo. Atha vā sundaraṃ ṭhānaṃ sammāsambodhiṃ nibbānameva vā gato adhigatoti sugato. Yasmā vā bhūtaṃ tacchaṃ atthasañhitaṃ vineyyānaṃ yathārahaṃ kālayuttameva ca dhammaṃ bhāsati, tasmā sammā gadatīti sugato, da-kārassa ta-kāraṃ katvā. Iti sobhanagamanatādīhi sugato, taṃ sugataṃ.
♦ Puññapāpakammehi upapajjanavasena gantabbato gatiyo, upapattibhavavisesā. Tā pana nirayādivasena pañcavidhā, tāhi sakalassāpi bhavagāmikammassa ariyamaggādhigamena avipākārahabhāvakaraṇena nivattitattā bhagavā pañcahipi gatīhi suṭṭhu mutto visaṃyuttoti āha – ‘‘gativimuttan’ ’ti. Etena bhagavato katthacipi gatiyā apariyāpannataṃ dasseti, yato bhagavā ‘‘devātidevo’ti vuccati, tenevāha –
♦ ‘‘Yena devūpapatyassa, gandhabbo vā vihaṅgamo;
♦ Yakkhattaṃ yena gaccheyyaṃ, manussattañca abbaje;
♦ Te mayhaṃ āsavā khīṇā, viddhastā vinaḷīkatā’ti. (a. ni. 4.36);
♦ Taṃtaṃgatisaṃvattanakānañhi kammakilesānaṃ aggamaggena bodhimūleyeva suppahīnattā natthi bhagavato gatipariyāpannatāti accantameva bhagavā sabbabhavayonigativiññāṇaṭṭhitisattāvāsasattanikāyehi suparimutto, taṃ gativimuttaṃ. Vandeti namāmi, thomemīti vā attho.
♦ Atha vā gativimuttanti anupādisesanibbānadhātuppattiyā bhagavantaṃ thometi. Ettha hi dvīhākārehi bhagavato thomanā veditabbā – attahitasampattito, parahitapaṭipattito ca. Tesu attahitasampatti anāvaraṇañāṇādhigamato, savāsanānaṃ sabbesaṃ kilesānaṃ accantappahānato, anupādisesanibbānappattito ca veditabbā. Parahitapaṭipatti lābhasakkārādinirapekkhacittassa sabbadukkhaniyyānikadhammadesanāto, viruddhesupi niccaṃ hitajjhāsayato, ñāṇaparipākakālāgamanato ca. Sā panettha āsayato payogato ca duvidhā parahitapaṭipatti, tividhā ca attahitasampatti pakāsitā hoti. Kathaṃ? ‘‘Karuṇāsītalahadayan’ti etena āsayato parahitapaṭipatti, sammā gadanatthena sugata-saddena payogato parahitapaṭipatti, ‘‘paññāpajjotavihatamohatamaṃ gativimuttan’ti etehi catusaccapaṭivedhatthena ca sugata-saddena tividhāpi attahitasampatti, avasiṭṭhena, ‘‘paññāpajjotavihatamohataman’ti etena ca sabbāpi attahitasampattiparahitapaṭipatti pakāsitā hotīti.
♦ Atha vā tīhākārehi bhagavato thomanā veditabbā – hetuto, phalato, upakārato ca. Tattha hetu mahākaruṇā, sā paṭhamapadena nidassitā. Phalaṃ catubbidhaṃ – ñāṇasampadā, pahānasampadā, ānubhāvasampadā, rūpakāyasampadā cāti. Tāsu ñāṇappahānasampadā dutiyapadena saccappaṭivedhatthena ca sugata-saddena pakāsitā honti. Ānubhāvasampadā tatiyapadena, rūpakāyasampadā yathāvuttakāyagamanasobhanatthena sugata-saddena, lakkhaṇānubyañjanapāripūriyā (dī. ni. 2.33; 3.198-200; ma. ni. 2.385-386) vinā tadabhāvato. Upakāro antaraṃ abāhiraṃ karitvā tividhayānamukhena vimuttidhammadesanā, so sammā gadanatthena sugata-saddena pakāsito hotīti veditabbaṃ.
♦ Tattha ‘‘karuṇāsītalahadayan’ti etena sammāsambodhiyā mūlaṃ dasseti. Mahākaruṇāsañcoditamānaso hi bhagavā saṃsārapaṅkato sattānaṃ samuddharaṇatthaṃ katābhinīhāro anupubbena pāramiyo pūretvā anuttaraṃ sammāsambodhiṃ adhigatoti karuṇā sammāsambodhiyā mūlaṃ. ‘‘Paññāpajjotavihatamohataman’ti etena sammāsambodhiṃ dasseti. Anāvaraṇañāṇapadaṭṭhānañhi maggañāṇaṃ, maggañāṇapadaṭṭhānañca anāvaraṇañāṇaṃ ‘‘sammāsambodhī’ti vuccatīti. Sammā gadanatthena sugata-saddena sammāsambodhiyā paṭipattiṃ dasseti, līnuddhaccapatiṭṭhānāyūhanakāmasukhallikattakilamathānuyoga- sassatucchedābhinivesādiantadvayarahitāya karuṇāpaññāpariggahitāya majjhimāya paṭipattiyā pakāsanato sugata-saddassa. Itarehi sammāsambodhiyā padhānāppadhānabhedaṃ payojanaṃ dasseti. Saṃsāramahoghato sattasantāraṇañcettha padhānaṃ payojanaṃ, tadaññamappadhānaṃ. Tesu padhānena parahitappaṭipattiṃ dasseti, itarena attahitasampattiṃ, tadubhayena attahitāya paṭipannādīsu (pu. pa. 24, 173) catūsu puggalesu bhagavato catutthapuggalabhāvaṃ dasseti. Tena ca anuttaradakkhiṇeyyabhāvaṃ uttamavandanīyabhāvaṃ, attano ca vandanakiriyāya khettaṅgatabhāvaṃ dasseti.
DN-t 1, Ganthārambhakathāvaṇṇanā, para. 28
MN-t 1, Ganthārambhakathāvaṇṇanā, para. 28
AN-t 1, Ganthārambhakathāvaṇṇanā, para. 41
Vism.
Explanation from the Visuddhimagga, pp. 198-199:
He is called sugata (i) because of a manner of going that is good (sobhaṇa-gamana), (ii) because of being gone to an excellent place (sundaraṃ ṭhānaṃ gatattā), (iii) because of having gone rightly (sammāgatattā), and (iv) because of enunciating rightly (sammāga-dattā).
(i) A manner of going (gamana) is called 'gone' (gata), and that in the Blessed One is good (sobhaṇa), purified, blameless. But what is that? It is the noble path; for by means of that manner of going he has 'gone' without attachment in the direction of safety—thus he is sublime (sugata) because of a manner of going that is good.
(ii) And it is to the excellent (sundara) place that he has gone (gata), to the deathless nibbana—thus he is sublime (sugata) also because of having gone to an excellent place.
(iii) And he has rightly (sammā) gone (gata), without going back again to the defilements abandoned by each path. For this is said: 'He does not again turn, return, go back, to the defilements abandoned by the stream-entry path, thus he is sublime ... he does not again turn, return, go back, to the defilements abandoned by the Arahant path, thus he is sublime' (old commentary?). Or alternatively, he has rightly gone from the time of [making his resolution] at the feet of Dipahkara up till the Enlightenment Session, by working for the welfare and happiness of the whole world through the fulfilment of the thirty perfections and through following the right way without deviating towards either of the two extremes, that is to say, towards eternalism or annihilationism, towards indulgence in sense pleasures or self-mortification—thus he is sublime also because of having gone rightly.
(iv) And he enunciates (gadati) rightly (sammā); he speaks only fitting speech in the fitting place—thus he is sublime also because of enunciating rightly.
Note also that this compound is used in the sense "fortunate destination" in DN 2-13:
So dibbena cakkhunā visuddhena atikkantamānusakena satte passati cavamāne upapajjamāne hīne paṇīte suvaṇṇe dubbaṇṇe sugate duggate
(Ven. Bodhi) With the divine eye, which is purified and surpasses the human, he sees beings passing away and reappearing—inferior and superior, beautiful and ugly, fortunate and unfortunate
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(Maurice Walshe) With the divine eye, purified and surpassing that of humans, he sees beings passing away and arising: base and noble, well-favoured and ill-favoured, to happy and unhappy destinations