The “curtal friar,” Friar Tuck, of the Robin Hood ballads, was merely so called because the frock worn by the friar was short, curtal being derived from the Latin curtus, “short.”
Other things were also “curtal” four hundred years ago, especially a horse whose tail had been bobbed, a “bobtailed horse,” we would say now.
And just through this association of curtal and tail, pronunciation and spelling were altered and remained altered to curtail.
