As covered elsewhere in this atlas, Greek settled into the alphabet used today only in 403 BCE, when Athens formally adopted the Ionic script; the cursive, rounded lowercase letters, beta included, came later still, standardised during the Byzantine minuscule reform of roughly the 9th century CE. Beta's modern technical senses are recent by comparison.
Ernest Rutherford named the electron emitted in radioactive decay a beta particle in 1899, the second stage in his alpha, beta, gamma classification of radiation by penetrating power; astronomers, following the Bayer star-naming convention of 1603, typically call the second-brightest star in a constellation Beta; and software makers, extending the same alpha-first sequence, call a more finished but still unreleased test version a beta, the stage of public or semi-public testing that follows internal alpha testing. Statisticians also use lowercase beta for a regression coefficient and for the probability of a false negative in hypothesis testing. None of these senses is older than the 17th century at the earliest, and the 19th and 20th century ones share nothing with beta's ancient Semitic or Kabbalistic background beyond the borrowed name.