This is the 9537th most frequent Russian word.
фейхой
"Фейхой" is a misspelling of "фейхоа," which refers to feijoa, a green, oval-shaped tropical fruit.
Here, фейхой is the instrumental case of the singular noun, used after the verb 'попробовать' to indicate the manner or means of an action.
Я попробовал фейхой впервые вчера.
I tried feijoa for the first time yesterday.
In this sentence, фейхой takes the genitive case in singular, indicating the substance or origin of the jam.
Это варенье сделано из фейхой.
This jam is made from feijoa.
Here, фейхой is in the instrumental case in singular form, used after the preposition 'с' to express inclusion in an action.