E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
and Tarpaulings. Soldiers and sailors. Soldiers are now
popularly called lobsters, because they are turned red when
enlisted into the service. But the term was originally applied
to a troop of horse soldiers in the Great Rebellion, clad in
armour which covered them as a shell. Sir William Waller
received from London (in 1643) a fresh regiment of 500 horse,
under the command of Sir Arthur Haslerig, which were so
prodigiously armed that they were called by the kings party the
regiment of lobsters. because of their bright iron shells with
which they were covered, being perfect cuirassiers, and were the
first seen so armed on either side.Clarendon: History of the
Rebellion, iii. 91.