From The Collaborative International Dictionary of English v.0.48:
Pore \Pore\, v. i. [imp. & p. p. Pored; p. pr. & vb. n.
Poring.] [OE. poren, of uncertain origin; cf. D. porren to
poke, thrust, Gael. purr.]
To look or gaze steadily in reading or studying; to fix the
attention; to be absorbed; -- often with on or upon, and now
usually with over."Painfully to pore upon a book." --Shak.
[1913 Webster]
The eye grows weary with poring perpetually on the same
thing. --Dryden.
[1913 Webster]