I have an Eldert Abraham FONDA, b. 1789 Father:Abraham Janse FONDA Mother:Annatie Osterhout FORT who married Elizabeth Wheeler and had a daughter Margaret b. Aug 1829 d. 19 Dec 1830 bur. Fonda Cemetery (Dennie's Hollow), Mayfield, Fulton Co., New York http://www.fonda.org/gedpage/fam/fam00323.htmhttp://www.fonda.org/gedpage/fam/fam00323.htm
And a separate Eldart Cornelius FONDA, b. 16 Nov 1800 Father:Cornelius Janse FONDA Mother:Catherina Fonda VIELE who married Marietta b. 1806 and had 5 children Olive 1836, Eldert 1838, Martha 1841, Oerin 1845 and Emily 1849 per 1850 U.S. Census, New York, Saratoga, Edinburgh http://www.fonda.org/gedpage/fam/fam01311.htmhttp://www.fonda.org/gedpage/fam/fam01311.htm
I don't have any documentation beyond that, but I guess it is possible that these two entries are the same person.