mammatus

Etymology
From.

Etymology
.

Adjective

 * 1) like mammalian breasts
 * 2) furnished with nipples, bumps, bulges or little pipes

Usage notes
"Tegula mammata" was a Roman architectural term referring to a type of tile that had conical projections or bosses on the wall-facing side, thus creating a hollow space underneath when installed. This void was used in wall heating systems to circulate hot air.