A couple of the Beech trees near here have these X’s on them.
There are very few English words that start with X – the least amount of any letter. Many of the words that do start with X are either standardized trademarks (Xerox) or acronyms (XC). No words in the Basic English vocabulary begin with ‘X’, but it occurs in words beginning with other letters.
X is the third least common letter in English, with a frequency of about 0.15% in words. It is, however, more frequent than Q and Z. Source: Wikipedia.