Can't tell you the origin, but there were plenty of Yopps in England going back at least as far as the sixteenth century. The name had a number of variants: Yop, Yopp, Yoppe, Yapp and Yappe. It settled eventually on 'Yapp' in England. Most of the ones we have found are in Shropshire, England, or close by. Have a look at the Clunbury Parish records for some examples:
https://ia700408.us.archive.org/35/items/registersofclunb38c... 1576 Aug 5 Fraunces d. of William Yoppe bap.
1602 Jan 30 [Elizab]eth, d of Rees Yoppe bap.
1602 Feb 3 _______ Yoppe bur.
1602 Feb 26 Johan Yoppe bur.
1624 Riceus Yopp et Elizabeth Beddoes mar.
1624 Mar 20 Sara f. Rice Yopp bap.
1629 Jan 28 the wife of John Yoppe bur.
1641 Apr 10 William Yoppe bur.
1644 Aug 23 Katherine Yoppe bur.
1644 Oct 3 Elianor Yoppe bur.
1645 Jan 22 Maria Yoppe bur.
1646 May 5 John Yoppe bur.
1652 Dec 3 Ann Yapp, wid. Bur
1691 Sep 8 Edward s. of Charles Yopp & Philadelphia bap.
1699 May 7 Hannah d. of Charles Yopp and Phelice bap.
1711 June 16 Mary d of Charles Yop bur.
1719 Mar 1 William Palmer and Mary Yop mar.
1726 Apr 25 Francis Yop bur.
1737 Jul 24 Thomas s of William Yapp and Elizabeth bap.
1737 Sep 3 Thomas s of William Yapp and Elizabeth bur
1738 Sep 10 John s of William Yapp and Elizabeth bap.
1740 Apr 13 Elizabeth d of William Yapp and Elizabeth bap.