Final answer:
The engine bottom end is commonly referred to as the crankshaft, which converts the reciprocating motion of the pistons into rotational motion.
Step-by-step explanation:
The engine bottom end is commonly referred to as the crankshaft. The crankshaft is responsible for converting the reciprocating motion of the pistons into rotational motion, which is then transferred to the wheels of the vehicle. It is an integral component of the engine and is vital for its operation.