Many people think, this euphemism for having sex, is based on the analog of a metal screw and how a guy seems to be driving that screw in, when experiencing
intercourse... but few realize at its start it was a farm expression, and describes the shape that many beast penises take when erect... such as pigs. Which also explains why we have the phrase, 'porking'.
Unconsciously perhaps, this also accounts for why sex is so exciting (beastal,
animalistic, natural, basic, lower brained, automatic, lust driven, unintellectual, etc. ) and so
disrespected.... same reasons as just stated for exciting.