The source of this word is Latin siphon, which is itself derived from Greek σίϕων ‘pipe’ or ‘tube’; the English word should therefore be spelled siphon. But it’s not quite that simple. This is because, during the 17th century, it began to be spelled syphon in an attempt to reflect its Greek etymology more closely. This was part of a general move to classicize English spelling, which saw pigmy change to pygmy, fisik change to physic, and stile to style. This last example was a change too far, however, since the word stile is actually from Latin stilus ‘writing instrument’ and has nothing to do with Greek στῦλος, which means ‘column’. The shift from siphon to syphon was similarly misguided, since the Greek word from which it derives was spelled with iota rather than upsilon. Etymologically, therefore, the spelling should be siphon; however the incorrect syphon spelling is now widely accepted and frequently features as a variant spelling in dictionaries. Discussion forums record opposing views, with some claiming that syphon is the British equivalent of US siphon, and others preferring syphon on aesthetic grounds. Both spellings are common on Twitter, with only a handful of people chastising those who use syphon; since one of these tweets under the Twitter handle @slyphon, he could be accused of having a vested interest.