lac.

From lact by simplification of a word-final sequence of two plosives (the variant nominative/accusative form lacte shows the addition of a vowel as an alternative). The etymology is controversial: there is no consensus on the cognate set, the manner of descent (inheritance vs. borrowing), or the form and ultimate origin of the etymon. Possible cognates include Ancient Greek γάλα (gála, “milk”, stem γᾰ́λᾰκτ- (gắlăkt-)), Old Armenian կաթն (katʻn, “milk”) and its likely variant *կաղց (*kałcʻ), Hittite 𒂵𒆷𒀝𒋻 (galaktar, “balm, resin”), Albanian dhallë (“buttermilk”), Romanian zară (“buttermilk”) and Waigali zōr (“milk”). More information Pokorny reconstructs the Latin and Greek words as inherited from Proto-Indo-European *glakt n from a root *glag- or *glak-. De Vaan derives the Latin, Greek and Armenian forms from Proto-Indo-European *gl̥gt-, and follows Meiser in explaining the loss of initial *g- in Latin as a result of long-distance dissimilation. Per Nielsen, the Latin and Greek words can be derived from *glakt-, Old Armenian *կաղց (*kałcʻ) can be derived from *g(a)l(ḱ)t- (requiring an initial non-palatal velar), and Albanian dhallë can perhaps be derived from *ǵal(K)- (requiring an initial palatal velar); on the basis of the variability in the initial consonant and the unusual root structure, Nielsen considers the root to be non-Indo-European in origin. Garnier, Sagart and Sagot 2017 attempt to derive the term from the root *h₂melǵ- (“milk”), instead: citing Garnier 2016's reconstruction of a verb *ambi-blactāre (“to milk with both hands”) > *amblactāre, they suppose that it was subsequently reanalyzed as *amb-lactāre > lactāre, which subsequently yielded the noun lact (> lac) via back-formation. For another possible relation, see dulcis.