smelling n.

c. 1200, smellen, "emit an odor; perceive an odor" (transitive and intransitive), "use the sense of smell, inhale the odor of," not found in Old English, perhaps cognate with Middle Dutch smolen, Low German smelen "to smolder" (see smolder). However, OED writes that it is "no doubt of Old English origin, but not recorded, and not represented in any of the cognate languages." Related: Smelled or smelt; smelling.

The figurative sense of "perceive as if by smell" is from late 14c. Specifically as "smell bad, stink" by late 14c. Smell-feast (n.) "one who finds and frequents good tables, one who scents out where free food is to be had" is from 1510s ("very common" c. 1540-1700, writes OED). To smell a rat "be suspicious" is from 1540s (see rat (n.)).