Comment by falsedan

Although interestingly enough from 'man ascii', it's clear why ^C is ETX:

  >         Oct   Dec   Hex   Char                        Oct   Dec   Hex   Char
  >         ────────────────────────────────────────────────────────────────────────
  >         000   0     00    NUL '\0'                    100   64    40    @
  >         001   1     01    SOH (start of heading)      101   65    41    A
  >         002   2     02    STX (start of text)         102   66    42    B
  >         003   3     03    ETX (end of text)           103   67    43    C
  >         004   4     04    EOT (end of transmission)   104   68    44    D
  >         005   5     05    ENQ (enquiry)               105   69    45    E

Holding Ctrl set bit 6 to '0', bit 7 to '1', and bit 8 to '0'. 'C' and 'c' differ by bit 6 only ('1' for 'c').