What does ache mean?
The definition of ache
Ache, n.
Etym: [OE. ache, AS. æce, ece, fr. acan to ache. See Ache, v. i.]

Continued pain, as distinguished from sudden twinges, or spasmodic pain. “Such an ache in my bones.” Shak.

Note: Often used in composition, as, a headache, an earache, a toothache.

Ache, v. i.
[imp. & p. p. Ached; p. pr. & vb. n. Aching.] Etym: [OE. aken, AS. acan, both strong verbs, AS. acan, imp. oc, p. p. acen, to ache; perh. orig. to drive, and akin to agent.]

To suffer pain; to have, or be in, pain, or in continued pain; to be distressed. “My old bones ache.” Shak. The sins that in your conscience ache. Keble.