The Hebrew and Greek that is translated as “thief” in English is translated in Low German as Spitzboov or “naughty boy” (translation by Johannes Jessen, publ. 1937, republ. 2006).
Following are a number of back-translations of Luke 12:39:
Nyongar: “And you already know this truth: if a man owns his house and he knows when the thief will come, he will not allow the thief to break his house and enter it.” (Source: Warda-Kwabba Luke-Ang)
Uma: “‘Store my parable in your hearts: If the house-owner knows ahead-of-time what time robbers will come, he will definitely guard so that they do not enter.” (Source: Uma Back Translation)
Yakan: “But remember this, that if the owner of a house knew at what time the thief will arrive he would certainly watch/stay awake and he would not let/abandon his house to be broken into and entered.” (Source: Yakan Back Translation)
Western Bukidnon Manobo: “And Jesus said again, ‘Don’t you forget that if the owner of the house knew when the thief would come, he would have carefully be on guard and that thief could not have entered into his house.” (Source: Western Bukidnon Manobo Back Translation)
Kankanaey: “‘Remember this also: if the house owner had known the hour that the thief would arrive, he would have been prepared so the thief would not have-been-able-to-enter.” (Source: Kankanaey Back Translation)
Tagbanwa: “Consider this. Supposing a householder knew at what hour a thief would come, of course he wouldn’t just allow his house to be entered.” (Source: Tagbanwa Back Translation)
Kabwa: “If a house owner would know the time when a thief is coming, he would prepare himself, and the thief would not enter inside his house.”
Suba-Simbiti: “If only a house owner would know the time at which a thief would come, he would prepare himself. He would not sleep, leaving the thief destroying his house.” (Source for this and above: R.M. Mészároš in Journal of Translation 18/2022, p. 115ff. )