Sneeze
Middle English: apparently an alteration of Middle English fnese due to misreading or misprinting (after initial fn- had become unfamiliar), later adopted because it sounded appropriate.
wiktionary
From Middle English snesen(“to sneeze”), alteration of earlier fnesen(“to sneeze”), from Old English fnēosan(“to snort, sneeze”), from Proto-West Germanic *fneusan, from Proto-Germanic *fneusaną(“to sneeze, snort”), from Proto-Indo-European *pnew-(“to breathe, pant, snort, sneeze”). Cognate with dialectal Dutch fniezen(“to sneeze”), Old Norse fnýsa(“to snort”).
Compare neeze, from Middle English nesen, from Old English *hnēosan(“to sneeze”), cognate to Old Norse hnjósa(“to sneeze”), Old High German niosan(“to sneeze”).
It has been suggested that the change could be due to a misinterpretation of the uncommon initial sequence fn- as ſn- (sn- written with a long s), [1] [2] [3] although the change is regular, seen also in snore and snort from Middle English fnoren and fnorten, and in late Middle English snatted from earlier Middle English fnatted(“snub-nosed”). The fn- forms of all these words fell out of use in the 1400s.
etymonline
sneeze (v.)
late 15c., from Old English fneosan "to snort, sneeze," from Proto-Germanic *fneusanan (compare: Middle Dutch fniesen, Dutch fniezen "to sneeze;" Old Norse fnysa "to snort;" Old Norse hnjosa, Swedish nysa "to sneeze;" Old High German niosan, German niesen "to sneeze"), from Proto-Germanic base *fneu-s- "sneeze," of imitative origin, as is PIE *pneu- "to breathe" (source of Greek pnein "to breathe").
Other imitative words for it, perhaps in various ways related to each other, include Latin sternuere (source of Italian starnutare, French éternuer, Spanish estornudar), Breton strevia, Sanskrit ksu-, Lithuanian čiaudėti, Polish kichać, Russian čichat'.
English forms in sn- might be due to a misreading of the uncommon fn- (represented in only eight words in Clark Hall, mostly in words to do with breathing), or from Norse influence. OED suggests Middle English fnese had been reduced to simple nese by early 15c., and sneeze is a "strengthened form" of this, "assisted by its phonetic appropriateness." Related: Sneezed; sneezing. To sneeze at "to regard as of little value" (usually with negative) is attested from 1806.
sneeze (n.)
"act of sneezing," 1640s, from sneeze (v.).
