Calcaneus - calcar, spur.⏎
Arytenoid - arytaina, pitcher; the two cartilages, with the gap between them, look like the spout of a pitcher.⏎
Callosum - callus, hard.⏎
Adrenal - ad, toward + ren, kidney.⏎
Acetabulum - acteum, vinegar + abrum, holder. Small cup for vinegar, hence any small cup.⏎