The wooden training dummy Mokujin ("Wooden Person"), debuted in the second Tekken game, a Japanese fighting game franchise created by Namco (now Bandai Namco) in the mid-nineties.
The character Mokujin is an animated wooden training dummy having been brought to life through the mysterious forces that be, that he may be the random-fighting-style-character-of-all-fighting-games-archetype, that is his fighting style is a randomised imitation of that of the cast of the game. His basic appearance is that of a wooden humanoid statue, whose limbs are connected via joints and metal chains. He mostly remains the same unless taking on the fighting-style of Yoshimitsu, the Space Ninja of the series, where he will equip a deceptively sharp wooden blade.
This arboreal martial-arts manikin has kanji etched into his back, enumerating the amount of direct hits (punches and kicks) that he has received or performed, written with the character of 正 ("correct, straight, right"), but in Karate possibly signifying a direct punch (正拳, seiken). The Tekken Wikia seems to suggest that the character is due to its stroke-order being five, hence used for counts of five and thus five hits. He sports 10 of these in Tekken 3.
Wiktionary amongst other sources points towards its usage as a tally marker hence its usage in martial arts as such, thus poor Mokujin has been either marking his losses or victories on his back. We shall never know.