Where does “cicadin” come from?

cicadin (English) comes from English in, from Middle English in, from Old English in, from Proto-West Germanic *in.

cicadin (English): An anti-fungal agent; a peptide isolated from the Cicada flammata, a cicada

Definitions

cicadin traces back through two separate lines of ancestry.

Step	Language	Word	Meaning
1	English	in	Used to indicate location, inclusion, or position...
2	Middle English	in	Any kind of accomodation; particularly; A home or...
3	Old English	in	in; Alternative form of inn
4	Proto-West Germanic	*in	—

Step	Language	Word	Meaning
1	English	cicada	Any of several insects in the superfamily...
2	Latin	cicada	cicada, tree-cricket; vocative singular of...