There were seven original sins, later known as the seven deadly sins. They were pride, envy, wrath, sloth, greed, gluttony, and lust.
The first trial Felix went through, the House of Indulgence, was clearly centered on lust. The second trial, the House of Wrath, was even more self-explanatory.
With this sudden influx of information, he had learned the names of the remaining five trials, immediately making the connection to the Seven Sins.
However, why did the S-tier Malevolent Phantom require