Egyptian menchet		Phoenician lamedh		Greek lambda	Λ (λ)
... Wikipedia has no information regarding the origin of the Phoenician lamedh, but the Egyptian 'cloth' hieroglyph (menchet) is - I suggest - related to the 4 upside down sky pillars. I.e. the basic element of the 'covering' hieroglyph could have indicated darkness:

... The seventh tree is the oak, the tree of Zeus, Juppiter, Hercules, The Dagda (the chief of the elder Irish gods), Thor, and all the other Thundergods, Jehovah in so far as he was 'El', and Allah. The royalty of the oak-tree needs no enlarging upon: most people are familiar with the argument of Sir James Frazer's Golden Bough, which concerns the human sacrifice of the oak-king of Nemi on Midsummer Day.

The fuel of the midsummer fires is always oak, the fire of Vesta at Rome was fed with oak, and the need-fire is always kindled in an oak-log. When Gwion writes in the Câd Goddeu, 'Stout Guardian of the door, His name in every tongue', he is saying that doors are customarily made of oak as the strongest and toughest wood and that 'Duir', the Beth-Luis-Nion name for 'Oak', means 'door' in many European languages including Old Goidelic dorus, Latin foris, Greek thura, and German tür, all derived from the Sanskrit Dwr, and that Daleth, the Hebrew letter D, means 'Door' - the 'l' being originally an 'r'. Midsummer is the flowering season of the oak, which is the tree of endurance and triumph, and like the ash is said to 'court the lightning flash'. Its roots are believed to extend as deep underground as its branches rise in the air - Virgil mentions this - which makes it emblematic of a god whose law runs both in Heaven and in the Underworld ... The month, which takes its name from Juppiter the oak-god, begins on June 10th and ends of July 7th. Midway comes St. John's Day, June 24th, the day on which the oak-king was sacrificially burned alive. The Celtic year was divided into two halves with the second half beginning in July, apparently after a seven-day wake, or funeral feast, in the oak-king's honour ...

... In Plato's Timaeus, it is explained that the two bands that form the soul of the world cross each other like the letter Χ ... Tav is the last letter of the Hebrew word emet, which means truth. The midrash explains that emet is made up of the first, middle, and last letters of the Hebrew alphabet (Aleph, Mem, and Tav...). Sheqer (falsehood), on the other hand, is made up of the 19th, 20th, and 21st (and penultimate) letters. Thus, truth is all-encompassing, while falsehood is narrow and deceiving. In Jewish mythology it was the word emet that was carved into the head of the Golem which ultimately gave it life. But when the letter 'aleph' was erased from the Golem's forehead, what was left was 'met' - dead. And so the Golem died ...