Superstitious mumbo-jumbo, having NOTHING to do with the Torah/word of G-d!
History of the observance
In the long period which is reflected in Talmudic literature the observance of the Ninth Day of Av assumed a character of constantly growing sadness and asceticism. By the end of the second century or at the beginning of the third, the celebration of the day had lost much of its gloom. Rabbi Judah ha-Nasi was in favor of abolishing it altogether or, according to another version, of lessening its severity when the fast has been postponed from Saturday to Sunday (Talmud, Tractate Megillah 5b).
The growing strictness in the observance of mourning customs in connection with the Ninth Day of Av became pronounced in post-Talmudic times, and particularly in the darkest period of Jewish history, from the fifteenth century to the eighteenth.
Maimonides (twelfth century), in his Mishneh Torah, says that the restrictions as to the eating of meat and the drinking of wine refer only to the last meal before fasting on the Eighth Day of Av, if taken after noon, but before noon anything may be eaten (Hilchoth Ta'anith 5:8). Rabbi Moses of Coucy (thirteenth century) wrote that it is the universal custom to refrain from meat and wine during the whole day preceding the Ninth of Av (Sefer Mitzvoth ha-Gadol, Venice ed., Laws of Tishah B'Av, 249b). Rabbi Joseph Caro (sixteenth century) says some are accustomed to abstain from meat and wine from the beginning of the week in which the Ninth Day of Av falls; and still others abstain throughout the three weeks from the Seventeenth of Tammuz (Shulkhan Arukh, Orach Chayim 551).
A gradual extension of prohibitions can be traced in the abstention from marrying at this season and in other signs of mourning. So Rabbi Moses of Coucy says that some do not use the tefillin ("phylacteries") on the Ninth Day of Av, a custom which later was universally observed (it is now postponed until the afternoon). In this manner all customs originally designated as marks of unusual piety finally became the rule for all. (Wikipedia)