From kuzo (“cousin”) + -iĉo (“male”).
kuziĉo (accusative singular kuziĉon, plural kuziĉoj, accusative plural kuziĉojn)
The neologistic suffix -iĉo is controversial, but even among its proponents the word kuziĉo is commonly not recommended. The word kuzo traditionally already means “male cousin” even without the addition of the masculine suffix -iĉo, making the suffix redundant.
Many users of the term believe that the meaning of kuzo (and other gendered root words) should be made gender neutral, changing it to just “cousin”. Some other people that actively use it do not aim to change the traditional meaning of “kuzo”, but think the redundancy of -iĉo is preferable to the asymmetry between the forms kuzo (“male cousin”) and kuzino (“female cousin”).
See also Gender reform in Esperanto and its section Masculine suffixes on Wikipedia, and the article on -iĉ- in Esperanto.