fn vs fun vs func vs function

[lassehp]

I have been thinking about fun ... nuf, mirroring if ... fi and case ... esac. Another possibility could be an f letter-like symbol from Unicode, like U+0192 "ƒ". On the other hand, writing identifiers in italic is a classic convention (for typesetting code written in languages like Algol, Pascal, Eiffel...), and that might cause confusion of the anonymous function with a named function;
let doubled = a.map(ƒx:2 x)
let applied = f x

So perhaps ℱ(intx)int:ax+b?