From Old French *sourire*, a compound of the prefix *sou-* (from Latin *sub-*, "under, slightly") and *rire* ("to laugh"), itself from Latin *ridēre*. The sense of "smiling" as a gentler, lesser form of laughing is thus baked right into the word's structure.

The French often distinguish between a polite, social smile and a warm, genuine one. The phrase *sourire du bout des lèvres* ("to smile at the tip of one's lips") specifically describes a thin, insincere smile — a nuance English captures awkwardly at best. Note that *sourire* is also a noun (un sourire = a smile), making it doubly useful to learn.