> ap·ro·pos
>
> /ˌæprəˈpoʊ/ Show Spelled[ap-ruh-poh] Show IPA –adverb
>
> 1\. fitting; at the right time; to the purpose; opportunely.
>
> 2\. Obsolete. By the way. –adjective
>
> 3\. opportune; pertinent: apropos remarks. —Idiom
>
> 4\. apropos of, with reference to; in respect or regard to: apropos of the preceding statement.
Definition #4 is where the unix command stems from. The results returned are _in reference to_ the input argument.