In one of his prophecies, Isaiah describes G-d as “the giver of strength to the tired (yaef) and to those without energy an abundance of might” (Isaiah 40:29). The first part of this verse is paraphrased in a blessing we recite every morning: “Baruch atah, Hashem…ha’noten la’yaef koach.” It’s also commonly appended to the end of sefarim as the author’s way of saying that his ability to endure weariness while authoring the work came from above.
Another two biblical words that mean tired are “ayef” and “yagea.” In fact, the Modern Hebrew word for “tired” is not “yaef,” but “ayef” (which actually appears in the Bible a few more times than “yaef” does). Is there any difference between these three words?
Some explain that “yaef” and “ayef” are actually synonymous and are indicative of a linguistic phenomenon known as metathesis (that is, the transposition of sounds or letters in a word). Thus, “ayef” and “yaef” are really the same word, but the first two letters switch positions. Indeed, Rabbi Yishaya of Trani (1180-1250), an important Italian Talmudist known as the Rid, compares the case of “ayef”/“yaef” to another, well-known case of metathetical synonyms, “kesev”/“keves,” which both mean lamb.
Rabbi Shimon Schwab (1908-1995), however, takes a different approach. When discussing the morning blessing on G-d giving strength to the tired, Rabbi Schwab argues that the word “yaef,” as opposed to “ayef” is specifically used. He explains that while “ayef” and “yaef” denote two different degrees of tiredness: “ayef” is used to describe someone who’s tired but still retains some energy, while “yaef” is used to describe someone who’s so tired that he has exhausted all his energy.
Thus, when praising G-d as the giver of energy to the tired, we use the word “yaef” for maximum effect. In other words, not only does G-d strengthen those who are tired, He also energizes those who are completely exhausted.
Rabbi Shlomo Aharon Wertheimer (1866-1935) explains that “ayef” denotes extreme fatigue to the point of fainting. That’s why a borrowed meaning of “ayef” is “thirsty” (see Job 22:7 and Psalms 63:2) as the Radak notes in Sefer ha’Shorashim – because dehydration is generally what causes tired people to faint.
Rabbi Yosef of Saragossa (d. 1420), a student of Rabbi Nissim of Gerona (1320-1380), explains that “ayef” describes someone who’s tired after having repeatedly performed certain movements. In other words, the persistence of action wears him out. “Yagea,” in contrast, describes someone whose tiredness results from the speed of his actions. In other words, he has overexerted himself.
The Malbim writes that “ayef” describes tiredness that a person with natural low-energy levels experiences, while “yagea” describes tiredness that results from overexerting oneself. Hence the connection between “yagea” and “yaga” (he toiled).
So if you’re wary of weariness and want to avoid fatigue, remember that all energy comes from G-d. As one popular figure was wont to say, “Say your prayers, eat your Wheaties, take your vitamins, and you will never go wrong.”