The bat's form has become more refined over time. In the mid-19th century, baseball batters were known to shape or whittle their own bats by hand. This allowed there to be a wide variety in shape, size, and weight. For example, there were flat bats, round bats, short bats, and fat bats. Earlier bats were known to be much heavier and larger than today's regulated ones. During the 19th century, many shapes were experimented with, as well as handle designs. Today, bats are much more uniform in design.
Fungo bats aren’t typical bats like the ones Mike Trout takes with him to a game situation. Rather, they’re more of practice bats. The bats are specially made for coaches to utilize when testing the fielding of their players. For example, a coach would break out his or her fungo bat when he or she is looking to hit his or her shortstop a couple of ground balls or when he/she hits pop flies to the centerfielder.
A fungo bat is a specially designed bat used by baseball and softball coaches for practice. The etymology of the word fungo ( /ˈfʌŋɡoʊ/) is uncertain, but the Oxford English Dictionary suggests it is derived from the Scots fung: to pitch, toss, or fling.[26] A fungo is longer and lighter than a regulation bat, with a smaller diameter. The bat is designed to hit balls tossed up in the air by the batter, not pitched balls.[27] Typical fungo bats are 35 to 37 inches (89 to 94 cm) long and weigh 17 to 22 ounces (480 to 620 g). Coaches hit many balls during fielding practice, and the weight and length allow the coach to hit balls repeatedly with high accuracy. The small diameter also allows coaches to easily hit pop-ups to catchers and infielders along with ground balls due to better control of the barrel of the bat.

Many players "bone" their bats, meaning that before games, they rub their bats repeatedly with a hard object, believing this closes the pores on the wood and hardens the bat. Animal bones are a popular boning material, but rolling pins, soda bottles and the edge of a porcelain sink have also been used. Pete Rose had his own way of hardening his bats: he soaked them in a tub of motor oil in his basement then hung them up to dry.[25]
If fungoes are a ball tossed into the air by a batter and then struck as it comes down then a fungo bat is a baseball bat used for hitting fungoes. To go into more detail, a fungo bat is a long, lightweight baseball bat used by coaches (or parents) during pregame hitting or practice to help them hit grounders and pop flys with more consistency and less fatigue. To be one of the best in baseball, countless hours of practice are a must and fungo bats are intended for both infield and outfield practice. Plus, they help tremendously with control and accuracy so that coaches and parents can place a ball where they want when they want. 
For starters, we should clarify just what we’re talking about when we say fungo bat. Longer, lighter and thinner than a regulation bat (but a larger barrel), a fungo bat is typically 35 to 37 inches long, and weighs between 17 and 22 ounces. As David Allison wrote in the June 1978 edition of Country Journal, “A fungo bat looks to be a cross between a baseball bat and a broomstick.”