The Collaborative International Dictionary of English v.0.48:

Welsh \Welsh\, a. [AS. w[ae]lisc, welisc, from wealh a stranger,
   foreigner, not of Saxon origin, a Welshman, a Celt, Gael;
   akin to OHG. walh, whence G. w[aum]lsch or welsch, Celtic,
   Welsh, Italian, French, Foreign, strange, OHG. walhisc; from
   the name of a Celtic tribe. See Walnut.]
   Of or pertaining to Wales, or its inhabitants. [Sometimes
   written also Welch.]
   [1913 Webster]

   Welsh flannel, a fine kind of flannel made from the fleece
      of the flocks of the Welsh mountains, and largely
      manufactured by hand.

   Welsh glaive, or Welsh hook, a weapon of war used in
      former times by the Welsh, commonly regarded as a kind of
      poleax. --Fairholt. --Craig.

   Welsh mortgage (O. Eng. Law), a species of mortgage, being
      a conveyance of an estate, redeemable at any time on
      payment of the principal, with an understanding that the
      profits in the mean time shall be received by the
      mortgagee without account, in satisfaction of interest.
      --Burrill.

   Welsh mutton, a choice and delicate kind of mutton obtained
      from a breed of small sheep in Wales.

   Welsh onion (Bot.), a kind of onion (Allium fistulosum)
      having hollow inflated stalks and leaves, but scarcely any
      bulb, a native of Siberia. It is said to have been
      introduced from Germany, and is supposed to have derived
      its name from the German term w[aum]lsch foreign.

   Welsh parsley, hemp, or halters made from hemp. [Obs. &
      Jocular] --J. Fletcher.

   Welsh rabbit. See under Rabbit.
      [1913 Webster]