term:

Logrolling

logrolling n

[from the former American custom of neighbors assisting one another in rolling logs into a pile for burning]
: the practice of including in a legislative bill unrelated provisions to attract a wider base of support and insure passage of the bill as a whole

Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.