Pronounced, "FFFF-THOW", is code for when you see a woman whose hard nipples are protruding from her shirt but is too close to otherwise point it out unnoticed. Stands for, "Full Titty Hard-On".
FTHOTL is an acronym for Fuck The Houses On The Left.
It is a reference to a Social Housing development situated to the left of a popular (but yet to be officially sanctioned) drag strip, deliberately plagued with noise at night - arising out of disdain for the inhabitant's approach to child-rearing.