Hashtable versus hash-table
It seems a shame that iterate spells it "in-hashtable" when Common Lisp spells its type "hash-table", and the various functions "make-hash-table", "hash-table-p", "hash-table-count", etc. It's also spelled "hash-table" in the loop macro.
I would suggest adding "in-hash-table" as a synonym for "in-hashtable" and updating the documentation to use that hyphenated form consistent with Common Lisp itself. There's probably no need, though, to ever completely remove the old spelling, just to prefer the consistent one. Leaving it there means no existing code gets broken.
I can't count the number of times I've accidentally typed "in-hash-table" and grumbled when it failed! :-)