One of the nails of the fingers. To one’s finger-nails: completely, thoroughly.

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a. 1240.  Wohunge, in Cott. Hom., 281. Þat te blod wrang ut at tine finger neiles.

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1842.  Tennyson, Edwin Morris, 22.

                I call’d him Crichton, for he seem’d
All-perfect, finish’d to the finger nail.
    Ibid. (1884), Becket, III. i. He’s as like the King as fingernail to fingernail.

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1888.  Graphic, Summer, No. 21/1. I was a theosophist to my finger-nails.

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