It is often that a person’s tongue cut his throat.
Note: This might be more colorfully be said as: “It is often that a man’s tongue slit his own throat”. Note also that although the seanfhocal speaks of a “person” (duine), it goes on to refer to “his throat”. Much as in English (in the days before political correctness), when it is necessary to ascribe gender to a person or people, the masculine gender is used. This can be viewed as either giving the subject “the benefit of the doubt”, or as a subtle statement that males come closest to the non-descript (neuter) gender.