Easton's Bible Dictionary (1897)
In the title of Ps. 61, denotes the music of stringed instruments (1 Sam. 16:16; Isa. 38:20). It is the singular form of Neginoth.
Smith's Bible Dictionary (1863)
(stringed instruments), the singular of Neginoth. If occurs in the title of (Psalms 61:1) It is the general term by which all stringed instruments are described.
Hastings' Dictionary of the Bible (1898) & Schaff's Bible Dictionary
NEG'INAH (a stringed instrument), used in Ps. 61, title; the singular of "Neginoth."