Reconstruction:Proto-Celtic/siti-

Etymology
Possibly related to the adjective, but the short *i is unexpected; perhaps from a participle  before undergoing , though this law's application might have been too early for the change of *eh₁ to *ē to *ī in Proto-Celtic. If not, then possibly from instead.

MacBain compares 🇨🇬, from.

Noun

 * 1) length