Acus has several meanings including a "single-prong hairpin" or "needle and thread, " she says.

WSJ: On Pins and Needles: Stylist Turns Ancient Hairdo Debate on Its Head

Studying translations of Roman literature, Ms. Stephens says, she realized the Latin term "acus" was probably being misunderstood in the context of hairdressing.

WSJ: On Pins and Needles: Stylist Turns Ancient Hairdo Debate on Its Head