A good rule of thumb is that in most cases, when a term or catchphrase is made up that is not in the Bible, it takes on a life of its own and it will deviate from scripture somewhere down the line.
1. Trinity.
2. Discipling someone.
3. Accepting Jesus as personal savior.
4. 5 finger plan of salvation.
5. Slain by the Spirit.
6. Sacraments.
7. Judaizers.
These are a but a few non-scriptural phrases from different groups, you may or may not be not be familiar with all of them. They've all taken a life of their own, because they are not anchored in scripture.
As with all of them, Trinity tries to package up an idea into a pill and make it more digestible. Trinity is easier than to say than the Father, the Son, and the Holy Spirit, each and every time. But you see the cost of convenience. Best way to avoid these is to stick only with what the scriptures say explicitly.