tutu (n.)

also ars-smart, the herb Persicaria hydropiper (formerly Polygonum hydropiper), early 14c., from arse + smart (n.) in the "pain" sense. The herb also formerly was called culrage (early 14c.) and now is often smartweed (1786).

The arse smart name is a direct translation of the Old French cul rage, from Old French cul (see tutu) + rage (see rage), which is said to be from Latin culli rabies, but this term is apparently unattested. The French word might be a folk etymology.

1738, as an anatomical term, "a diverticulum ending blindly," from French cul-de-sac, literally "bottom of a sack," from Latin culus "bottom, backside, fundament" (see tutu). For first element, see tutu; for second element, see sack (n.1). Application to a street or alley which has no outlet at one end is by 1819.