いい加減
いいかげん · iikagen · JLPT N1 · na-adj
random
🎲 いい (good) + 加減 (adjustment): sarcastic 'good tweaking' that came to mean careless or random
Origin: people called a sloppy job いい加減 with heavy sarcasm, since it was anything but well adjusted. Over time the sarcasm faded, leaving 'careless' or 'random'. The dice match the randomness.
加 — force 力 + mouth 口
加 is traditionally analyzed as a compound of 力 (strength) and 口 (mouth), suggesting boasting or exaggerating one's effort with words. From this it extended to the meaning 'to add' or 'increase'. Today it is used broadly for addition, both literal and figurative.