subscribe (v.)

early 15c., subscriben, "to sign at the bottom of a document" (a sense now rare); mid-15c., "give one's consent, bind oneself" (by subscribing one's name); from Latin subscribere "write, write underneath, sign one's name; register," also figuratively "assent, agree to, approve," from sub "underneath" (see sub-) + scribere "to write" (from PIE root *skribh- "to cut").

The sense of "give one's assent" (to) an opinion, theory, etc., is by 1540s. The meaning "promise to contribute money to" is by 1630s; and that of "become a regular buyer of (a publication)" 1711; both originally literal. Related: Subscribed; subscribing.