seal [OE] Rather than signing their name, people formerly stamped a personal seal in wax on a completed letter or other document. The expressions put the seal on, ‘to put the finishing touch to something’, and set your seal to, ‘to mark something with your own distinctive character’, both derive from this. To seal something off reflects the use of seals to check that something has not been opened or disturbed. In these and related uses, seal goes back to Latin sigillum ‘small picture’, from signum ‘a sign’, the source of design [L16th], designate [M17th], ensign [LME], insignia [M17th], sign [ME], signal [LME], *scarlet, and numerous other English words. This seal dates from Middle English. The name of the animal seal derives from Old English seolh, the source also of the selkie or silkie [M16th], the mysterious seal woman of folklore.