This is the 7119th most frequent Russian word.
борису
"Борису" means "to Boris" (dative case of the name Борис).
The word 'борису' is used here in the dative case, which among other uses, indicates the indirect object of the action of calling.
Я позвонил Борису вчера вечером.
I called Boris yesterday evening.
In this sentence, 'борису' is also in the dative case, demonstrating the recipient of the action of presenting.
Подарок был вручён Борису на его день рождения.
The gift was presented to Boris on his birthday.
Here, 'борису' is in the dative case, used after the adjective 'благодарны' to indicate the person to whom gratitude is directed.