在给定的一段文本中找到并高亮显示出现频率最高的单词。


源文本：
In the early years of the 20th century, Einstein's theories, first published in 1905, had made him famous beyond scientific circles for his courageous willingness to question long-held beliefs. Then, in February 1919, astronomers studying a solar eclipse provided the first-ever experimental proof for one of his major predictions: that the sun's gravitational pull bends starlight, a triumph that made Einstein an overnight icon.
高亮显示出现频率最高的单词：Einstein。