I'd \I'd\ A contraction from I would or I had.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Id \Id\, n. (Zo["o]l.) A small fresh-water cyprinoid fish (Leuciscus idus or Idus idus) of Europe. A domesticated variety, colored like the goldfish, is called orfe in Germany.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Idem \I"dem\, pron. or adj. [L.]

The same; the same as above; -- often abbreviated id.

Source: Webster's Revised Unabridged Dictionary (1913)