A Hamish is both a sexual act and also a form of preemptive abortion. Rather than being inseminated and carrying a foetus to until child (see “Cum pet”) birth, one swallows the seamen. To get the full “Hamish” experience a red handkerchief is used by one of the parties, usually the receiver of the seamen.
I knew the guy I was seeing had a weird kink about cats and shoes, so when he was getting close I made sure there were no more pets to be involved and in between screams of pleasure yellowed out “ I’m not on birth control, how about doing a Hamish”