"a toad, a frog," late 14c., paddok (late 12c. as a surname), probably a diminutive of pad "toad," from Old Norse padda; from Proto-Germanic *pado- "toad" (source also of Swedish padda, Danish padde, Old Frisian and Middle Dutch padde "frog, toad," also Dutch schildpad "tortoise"), of unknown origin and with no certain cognates outside Germanic. Paddock-stool was an old name for a toadstool (mid-15c.). Pad in the straw was a 16c.-17c. expression meaning "something wrong, hidden danger."
"a small field or enclosure," 1620s, apparently an alteration of Middle English parrock, from Old English pearroc "enclosed space, fence" (see park (n.)). Or possibly from Medieval Latin parricus (8c.), which ultimately is from Germanic. Especially a small pastured enclosure near a stable.