kalla ekki allt ömmu sína

From the latter half of the 19th century; origins unclear but assumed to have originated as a joke making fun on someone who bragged about his family tree. Literally “doesn't refer to everything as his grandmother”.

kalla ekki allt ömmu sína

1. (idiomatic) to be unafraid of tackling a difficult task

   Hann kallar ekki allt ömmu sína en hann ætlar að hlaupa maraþon í sumar. ― He certainly doesn't flinch away from daunting tasks; he is planning on running a marathon this summer.

2. (idiomatic) not easily shocked; tough and resilient

• ráðast ekki á garðinn þar sem hann er lægstur
• láta ekkert á sig fá, karl í krapinu, óhræddur, ófeiminn, hörkutól, harðjaxl, enginn veifiskati, láta sér fátt fyrir brjósti brenna

• þar hitti skrattinn ömmu sína (“to meet someone equally or more stubborn than oneself”)