From prandium (“first meal, lunch”). The ending could be either the neuter diminutive suffix -culum or the "instrumental" noun suffix -culum. Either formation is unusual: the expected diminutive form from prandium is prandiolum, and the instrumental noun suffix -culum typically attaches to a verbal rather than a nominal base.

• (Classical Latin) IPA^(key): /pranˈdi.ku.lum/, [prän̪ˈd̪ɪkʊɫ̪ʊ̃ˑ]
• (modern Italianate Ecclesiastical) IPA^(key): /pranˈdi.ku.lum/, [prän̪ˈd̪iːkulum]

prandiculum n (genitive prandiculī); second declension

1. breakfast
   • Festus, De Verborum Significatione 250.42:

     Prandicula antiqui dicebant, quae nunc ientacula.

     The ancients called "prandicula" what we now call "ientacula".

Not attested in usage in antiquity, but mentioned in a passage by the grammarian Sextus Pompeius Festus as an antiquated term for the meal called iēntāculum (“breakfast”) in Classical Latin.

Second-declension noun (neuter).

• “prandiculum”, in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
• prandiculum in Gaffiot, Félix (1934) Dictionnaire illustré latin-français, Hachette.