In Lithuanian
It is the one of optative mood forms, which survived in Lithuanian language. For example, the permissive mood of verb tekù (to run) is teteka (let him run). This form has also meaning of third-person dual and plural. One of signs of permissive mood is prefix te of obscure origin; it is added (for primary verbs, which has bisyllabic stem in present tense and stressed ending in first-person present tense) to the form of third-person singular ancient optative mood or to the form of third-person singular indicative mood for the secondary verbs and for those primary verbs, which has unstressed ending in the first-person singular form (for example, the permissive mood of bégu is tebéga).
Read more about this topic: Permissive Mood