to sign one's name at the end of (a letter, document, etc.)
undersign in American English
(ˌundərˈsain, ˈundərˌsain)
transitive verb
to sign one's name under or at the end of (a letter or document); affix one's signature to
Word origin
[1570–80; under- + sign]This word is first recorded in the period 1570–80. Other words that entered Englishat around the same time include: bracket, cartridge, huddle, repeater, splitunder- is a prefixal use of under, as to indicate place or situation below or beneath (underbrush; undertow); lower in grade or dignity (undersheriff; understudy); of lesser degree, extent, or amount (undersized); or insufficiency (underfeed)