kalla ekki allt ömmu sína

Literally, “doesn't refer to everything as his grandmother”. 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.

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”)