The adjective ἑδραῖος (from ἕδρα, 'seat') originally meant 'seated' or 'sedentary,' but developed to mean firmly established, immovable, steadfast. In NT usage it describes the stability Paul urges in believers: settled purpose, unwavering resolve, immovable commitment to faith and service. The word suggests deep-rooted stability rather than mere stubbornness—like a building on solid foundation or a person planted in one place, unmoved by shifting winds.