μάτηνmátēn
GreekG31552 occurrences (KJV)
folly, i.e. (adverbially) to no purpose
KJV renders it: in vain
Where it appears
Lexical data: Strong’s Hebrew & Greek Dictionaries (1890, public domain; openscriptures, CC-BY-SA). Word tagging from the Strong’s-numbered KJV.