Abarim Publications' online Biblical Hebrew Dictionary
The verb זבד (zabad) means to give or bestow. Its sole derivative is the masculine noun זבד (zebed), meaning gift.
Both the verb and the noun occur only once in the Bible, and both in the same scene where Leah is about to name her son Zebulun, and says, "God has endowed me with a good gift . . . " (Genesis 30:20).
Another, much more common verb that means to give is נתן (natan - hence the name Nathan). By the time the Bible was written in its present form, the verb זבד (zabad) was probably already rather old fashioned. But that it was once quite popular is argued by the array of different Biblical names that were derived from this verb, including Zebadiah and Zebedee. Names in a certain language tend to be older than the words used in that same language, and therefore commonly reflect an older version of that language.