Although the sixth sense is commonly used today to refer to psychic perception or ESP, it is not native in this way. Humans have five senses; Touch, smell, see, hear and taste. A sixth sense would simply be a meaning that goes beyond these five senses, usually an inexplicable one.
As mentioned, it was not originally thought of in terms of ESP. The term derives from a study conducted at the beginning of the 20th century on the visually impaired. It was observed and documented that some blind people placed in a room they had never been before could navigate the room without hitting objects in the room.
In other words, even if they could not see the objects, they might still find that the objects were there and avoid them. At that time, there was very little theory about how this was possible, so it was inexplicable. Therefore, the term "sixth sense" was coined to describe a meaning that went beyond the normal five senses.
Some recent studies suggest that this is not a sixth sense at all, but rather an acute sense of hearing. It should be noted, however, that there are deaf and blind people who are still able to navigate objects that are on their way, although they can not see or hear the sound objects reflected in them. For now, it remains inexplicable and it seems that they really could have a sixth sense.