もし
もし · moshi · JLPT N4 · adverb
if
moshi-moshi on the phone: IF anyone is there? One moshi = if
Sound hook, not true etymology: the phone greeting moshi moshi feels like asking if someone is on the line. Cut it to a single moshi and you have if. It usually pairs with a conditional ending like -tara or -nara later in the sentence.