Start on the pitch, because that is where the picture is clearest. A foul is what the referee calls when someone plays outside the rules — a shirt pulled, a leg put out, a hand where no hand should be — and foul play is playing that way. English then takes the same picture off the pitch. Wherever people are supposed to be dealing fairly and somebody is not, that is foul play. Police use it in one fixed way: when a death may have been caused by another person, they say they suspect foul play. Seeing the two together is a way to hold them in mind, not a claim about which one English used first.
From the picture
警方用語：死因可疑
同樣是「有人不照規矩來」，只是這次講的不是比賽，是一條人命，而且只用在一個固定的問題上：這個人的死，是不是別人造成的。這是幫助記憶的連結，不是在主張哪個意思先出現。
noun · C1
Crime as the reason for a death, especially killing. Police and reporters use the phrase while they are deciding whether another person caused the death.
他殺嫌疑
noun · B2
Action that breaks the rules — playing or dealing in a way that is unfair, dishonest, or against the law, especially during a game.
犯規；不正當行為