a la mode (adv.)

from French à la, literally "to the," hence "in the manner of, according to," from à, from Latin ad "to" (see ad-) + la, fem. of definite article le "the," from Latin ille (fem. illa; see le). Attested in English in French terms from fashion or cookery since late 16c.; since c. 1800 used in native formations with English words or names.

"current fashion, prevailing style," 1640s, from French mode "manner, fashion, style" (15c.), a specialized use of the French word that also yielded mode (n.1).