pamphlet (n.)

"small, unbound treatise," late 14c., pamflet, "brief written text; poem, tract, small book," from Anglo-Latin panfletus, which probably is a popular short form of "Pamphilus, seu de Amore" ("Pamphilus, or about Love"), a short 12c. Latin love poem popular and widely copied in the Middle Ages; the name from Greek pamphilos "loved by all," from pan- "all" (pam- before labials; see pan-) + philos "loving, dear" see -phile).

Meaning "brief work dealing with questions of current interest; short treatise or essay, generally controversial, on some subject of temporary public interest" is from late 16c.