early 13c., "hind part of a ship; steering gear of a ship," probably from a Scandinavian source, such as Old Norse stjorn "a steering," related to or derived from styra "to guide" (see steer (v.)). Or the word may come from Old Frisian stiarne "rudder," which also is related to steer (v.). Stern-wheeler as a type of steam-boat is from 1855, American English.
-ward
adverbial suffix expressing direction, Old English -weard "toward," literally "turned toward," sometimes -weardes, with genitive singular ending of neuter adjectives, from Proto-Germanic *werda- (cognates: Old Saxon, Old Frisian -ward, Old Norse -verðr), variant of PIE *werto- "to turn, wind," from root *wer- (2) "to turn, bend." The original notion is of "turned toward."