By samyama, one gains knowledge of the language of all beings.

Verse 3.17

शब्दार्थप्रत्ययामामितरेतराध्यासात्संकरः तत्प्रविभागसंयमात् सर्वभूतरुतज्ञानम् ॥१७॥

śabdārtha-pratyayāmām-itaretarādhyāsāt-saṁkaraḥ tat-pravibhāga-saṁyamāt sarvabhūta-ruta-jñānam ॥17॥

Words, objects and ideas are superimposed, creating confusion; by samyama, one gains knowledge of the language of all beings.

Verse 3.18

संस्कारसाक्षात्करणात् पूर्वजातिज्ञानम् ॥१८॥

saṁskāra-sākṣātkaraṇāt pūrva-jāti-jñānam ॥18॥

Through direct perception of his subliminal impressions, the yogi gains

knowledge of his previous lives.

Conventional usage of a word, its fundamental meaning, content and feeling may all coincide, or may be confused due to intermixture or superimposition.

The same word may convey altogether different meanings in another language.

A perfect yogi acquires accurate knowledge of the meaning and feeling of any sound or word, in any language produced by any being.

We do not ordinarily differentiate between a word, its original purpose and meaning, and its contemporary usage; they are considered by those of average intellect to coincide. A cultured intellect, however, may penetrate deeply to understand just what is conveyed by the sound, meaning and sense of a word. 

An accomplished yogi intuitively perceives and precisely distinguishes the meaning and feeling of each word or sound uttered by any living being, according to how they express themselves.

The yogi is able to recollect the impressions of past incarnations which have moulded his present life. In the continuity of life, instinct, memory and desire play important roles. 

Memory belongs to the subconscious mind, and the fruits of desires (pains and pleasures experienced in the present life as a result of good and bad actions in past lives) to the unconscious.

When a yogi is free from all instincts and desires, he sees directly, independent of memory, and of feelings of joy or sorrow. Through intuition, in the orderly sequence of time, he actually sees his past lineage and future status, and also the lives of others.

PATANJALI YOGA SUTRAS