Laudator Temporis Acti

Persius 1.56-57 (tr. Susanna Morton Braund):

You're a fool, baldy, your fat paunch sticking out with an overhang of a foot and a half.

                                   nugaris, cum tibi, calve,
pinguis aqualiculus propenso sesquipede extet.

Oleg Nitikinski on line 57 cites Galen, On the Preservation of Health 37 (παχεῖα γαστὴρ λεπτὸν οὐ τίκτει νόον) and Jerome, Letters 52.11 (pinguis venter non gignit sensum tenuem).

Entries for aqualiculus and related words in the Thesaurus Linguae Latinae (2:365-366): In other words, aqualiculus is derived from the word for a water pot. Cf. our pot-belly. Eugene S. McCartney, "Augustus Compares Horace to a Sextariolus," Classical Journal 44.1 (October, 1948) 55-56, gives "modern examples of names of containers of liquids used to describe persons, generally stout ones."

J.N. Adams, "Anatomical Terms Transferred from Animals to Humans in Latin," Indogermanische Forschungen 87.1 (1982) 90-109 (at 100):

Aqualiculus (lit. 'small vessel for water') was strictly used of the belly of a pig (Isid., Etym. 11.1.136 'aqualiculus . . . proprie porci est; hinc ad uentrem translatio'; cf. Marc. Emp. 12.56 'porcelli lactentis uentriculo, id est aqualiculo, exempto') and perhaps other quadrupeds (note Mul. Chir. 208 'primo de ipso uentre, quod est aqualiculo', 210 'facit extensionem uentris, id est aqualiculi dolorem ingentem', Veg., Mul. 1.40. l 'uenter ipse, qui aqualiculus nominatur'). For the metaphor, one might compare Paul. Fest. p. 279 'pertusum dolium cum dicitur, uentrem significat'. Aqualiculus is used pejoratively of a man's pot belly at Pers. 1.57 (cum tibi, calue, / pinguis aqualiculus propenso sesquipede extet'), but by the time of Marcellus Empiricus it could be applied inoffensively to the human belly (7.16, 20.86). Aqualiculus did not survive in the Romance languages.

Thanks very much to Juan Manuel Acquaroni Vidal for the following relevant entries in his Diccionario histórico de la lengua latina: