We don't have synonyms for fother yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are mother, other and father.
(n) :
a wagonload; a load of any sort; an old English measure of lead or other metals, usually containing 19.5 hundredweight; a fodder
"1866: Now measured by the old hundred, that is, 108 lbs. the charrus contains nearly 19 1/2 hundreds, that is it corresponds to the fodder, or fother, of modern times. &mdash"
(n) :
a wagonload; a load of any sort; an old English measure of lead or other metals, usually containing 19.5 hundredweight; a fodder
"1866: Now measured by the old hundred, that is, 108 lbs. the charrus contains nearly 19 1/2 hundreds, that is it corresponds to the fodder, or fother, of modern times. &mdash"