IPA: //ˈtrʌkjulənsi//
KK: /trʌkəˌlɛnsi/
A quality of being aggressive, fierce, or eager to fight; a tendency to be combative or hostile.
His truculency made it difficult for him to maintain friendships.
Truculency is derived from "truculentus" (meaning fierce or savage) in Latin, which itself comes from "trux" (meaning rough or savage). The suffix "-ency" (meaning the quality of) indicates a state or condition. Thus, truculency refers to the quality of being fierce or aggressive.
Think of 'truculent' meaning fierce or savage, and remember that 'truculency' describes the quality of being fierce.