The word “halevai” is found in both Modern Hebrew and Yiddish—and by extension English. It means “if only” and “I wish.”
Its source is in Aramaic spoken in the Holy Land in the times of the Second Temple, comparable to the Hebrew word “lu” used in Biblical Hebrew.
“Halevai Beinoni”
One can say that the word expresses a wish for something so wonderful that one almost dares not verbalize the desire. This is demonstrated in the following Chassidic anecdote:
Reb Hillel Paritcher was among the foremost Chassidim of the early Chabad rebbes, one of the few who composed Chassidic discourses of his own.
He once remarked that prior to his exposure to the Chassidic approach, he could have fancied himself a tzaddik, a righteous person, free of sin or blemish. However, after learning the Chabad approach, he now came to the realization that halevai beinoni, “if only I could be a middling [servant of G‑d].”