I am not familiar with the term "lek" so I looked a bit further and found this:

"The term derives from the Swedish lek, a noun which typically denotes pleasurable and less rule-bound games and activities ("play", as by children). Specifically, the etymology of the word "lek" is from 1871 and means to engage in courtship displays (of certain animals); probably from the Swedish leka "to play".[3]"


Wikipedia reference