Swell
Old English swellan (verb), of Germanic origin; related to German schwellen . Current senses of the noun date from the early 16th century; the informal adjectival use derives from noun swell (sense 5 of the noun) (late 18th century).
wiktionary
From Middle English swellen, from Old English swellan(“to swell”), from Proto-Germanic *swellaną(“to swell”), of unknown origin. Cognate with Old Frisian swella, Low German swellen, Dutch zwellen(“to swell”), German schwellen(“to swell”), Swedish svälla(“to swell”), Icelandic svella. The adjective may derive from the noun.
From Middle English swelle, from the verb swellen (modern swell).
From the noun "swell" (a person dressed in an elegant manner).
etymonline
swell (v.)
Old English swellan "grow or make bigger" (past tense sweall, past participle swollen), from Proto-Germanic *swellanan (source also of Old Saxon swellan, Old Norse svella, Old Frisian swella, Middle Dutch swellen, Dutch zwellen, Old High German swellan, German schwellen), which is of unknown origin, perhaps a substratum word. Of emotions from late 14c., of music from 1749. Related: swelled; swollen; swelling.
swell (n.)
c. 1200, "a morbid swelling," from swell (v.). In reference to a rise of the sea, it is attested from c. 1600; of music, by 1803. The meaning "wealthy, elegant person" is first recorded 1786, connected to the now-obsolete sense "pompousness, arrogance" (1724), both from the notion of "puffed-up" demeanor or behavior.
swell (adj.)
"fashionably dressed or equipped," 1810, from swell (n.) in the "stylish person" sense. As "good, excellent," by 1897; as a stand-alone expression of satisfaction it is recorded from 1930 in American English.
