Acetabulum - acteum, vinegar + abrum, holder. Small cup for vinegar, hence any small cup.⏎
Calcaneus - calcar, spur.⏎
Alveolus (alveolar) - alveolus, small compartment.⏎
Atrium - atrium, court or hall.⏎
Atlas - Atlas, mythical figure; Atlas supports the world on his shoulders.⏎