Some shit some crazy york niggas say, swearing on the timbs is the absolute highest degree of swearing on something, even higher than yo mamas grave deadass b, the worst part is once you start saying this shit youll never stop even if you dont got no fuckin timbs youll still be swearing on em....
An expressionusually used by chavs and the like who want to sound honest and trustworthy. Should (almost) always be interpreted as "I'm lying through my teeth".
"m8 i dont no were ur weed is i swear on me nans grave i dint steal it m8"
"kev i swear on me nans grave i aint never cheated on u"
see also: chav, charver