Where does “FSMdidit” come from?

FSMdidit (English) comes from English IT, from Middle English it, from Old English hit, from Proto-Germanic hit, from Proto-Indo-European ḱe- — demonstrative particle; here; this, here.

Ancestry of “FSMdidit”, step by step

FSMdidit traces back through two separate lines of ancestry.

via English IT

StepLanguageWordMeaning
1EnglishITInitialism of information technology; Initialism...
2Middle EnglishitAlternative form of hit
3Old Englishhitit
4Proto-Germanichitnominative/accusative singular neuter of *hiz
5Proto-Indo-Europeanḱe-demonstrative particle; here; this, here

via English DID

StepLanguageWordMeaning
1EnglishDIDInitialism of direct inward dialing; Initialism...
Every word from Proto-Indo-European ḱe-
FSMdidit — Etymology, Origin & Word History | Etymology Explorer