from
The Collaborative International Dictionary of English v.0.48
Perk \Perk\ (p[~e]rk), v. t. [imp. & p. p. {Perked} (p[~e]rkt);
p. pr. & vb. n. {Perking}.] [Cf. W. percu to trim, to make
smart.]
To make trim or smart; to straighten up; to erect; to make a
jaunty or saucy display of; as, to perk the ears; to perk up
one's head. --Cowper. --Sherburne.
[1913 Webster]
{to perk up one's ears} to begin to listen attentively; --
usually used when something of interest is mentioned in
some discourse, after one's attention had lapsed; as, he
perked up his ears when he heard his name mentioned.
[PJC]