Lewis & Short

spĕcillum, i, n. [specio], a surgical instrument for examining diseased parts of the body, a probe, Cic. N. D. 3, 22, 57; Cels. 5, 28, 12; 7, 8; 6, 9 med.; Plin. 7, 53, 54, § 183; 32, 7, 24, § 75.