to all electric apparatus."

The latter observation may explain a common folk etymology of the
term; that it came from telephone company usage, in which "bugs in
a telephone cable" were blamed for noisy lines. Though this
derivation seems to be mistaken, it may well be a distorted memory
of a joke first current among *telegraph* operators more than
a century ago!

Or perhaps not a joke. Historians of the field inform us that the
term "bug" was regularly used in the early days of telegraphy to
refer to a variety of semi-automatic telegraphy keyers that would
send a string of dots if you held them down. In fact, the
Vibroplex keyers (which were among the most common of this type)
even had a graphic of a beetle on them! While the ability to send
repeated dots automatically was very useful for professional morse
code operators, these were also significantly trickier to use than
the older manual keyers, and it could take some practice to ensure
one didn't introduce extraneous dots into the code by holding the
key down a fraction too long. In the hands of an inexperienced
operator, a Vibroplex "bug" on the line could mean that a lot
of garbled Morse would soon be coming your way.

Actually, use of `bug' in the general sense of a disruptive event
goes back to Shakespeare! In the first edition of Samuel Johnson's
dictionary one meaning of `bug' is "A frightful object; a
walking spectre"; this is traced to `bugbear', a Welsh term for
a variety of mythological monster which (to complete the circle)
has recently been reintroduced into the popular lexicon through
fantasy role-playing games.