Words related to -er
Old English bettra, earlier betera "of superior quality or excellence," from Proto-Germanic *batizo-, perhaps from PIE *bhad- "good," but Boutkan finds no good IE etymology. For etymology and evolution, see best. Cognate words also have become the comparative adjective of good in the older Germanic languages (Old Frisian betera, Old Saxon betiro, Old Norse betr, Danish bedre, Old High German bezziro, German besser, Gothic batiza). All are comparatives of a positive (Proto-Germanic *bat) which is not in use.
In Middle English the adverbial form commonly was bet, sometimes also was an adjective; bet was displaced by c. 1600. From late Old English as "improved in health, more healthy" (adv.); from late 12c. as "more useful or desirable." Better half "wife" is first attested 1570s.
late 14c., "one who forwards or advances" (the interest of someone or some cause), "supporter," agent noun from promote, and also from Old French promotor, promoteur and directly from Medieval Latin promotor.
Specific financial sense of "one who leads in forming a company" is from 1876; sense of "one who organizes sporting or entertainment events" is attested from 1936. In late Middle English and early Modern English it also had a sense of "an informer," from promote in a 15c. sense of "inform against."
c. 1400, sailer, "one who sails," agent noun from sail (v.). The spelling with -o-, erroneous but now established, arose 16c., probably by influence of tailor, etc., and to distinguish the meaning "seaman, mariner" from "thing that sails."
It replaced much older seaman and mariner (q.q.v.), and its later appearance is perhaps to avoid confusion with common Middle English saillour, sailer "dancer, tumbler, acrobat" (mid-13c. as a surname), from Old French sailleor (from Latin salire "to leap"). Old English also had merefara "sailor."
Applied as an adjective from 1870s to clothing styles and items based on a tailor's view of a sailor's characteristic attire. Vulgar extended form sailorman is by 1761. Sailor's purse "egg pouch of a ray or shark" is so called by 1874; it is typically empty when found on shore.