I can't remember now if it was Madeleine Bassett or Gussie Fink-Nottle who was so described, and I don't have the works to hand.

I wonder if he picked it up in the US, or whether he introduced it over there from the UK.

If it was one of those two (I don't have the books here either) then it would have been Madeleine Bassett.

Calling someone a pill is dated now but definitely of UK origin. As you would imagine it is usually used to refer to someone whose behaviour is hard to swallow. Is it a simile or a metaphor? Neither seems quite right somehow.