BTW, why do UK/Germany start with "E", but France/Switzerland with "L"?
E is Northern Europe
L is for Latin Europe (eg those countries closer to the Mediterranean)
Incidentally, the EGXX identifiers work like this
EGLL (for London Airport) is a 'mother' aerodrome, whilst EGLD (Denham) is a 'daughter'. I think this dates back to the time when telex messages were sent to a main aerodrome for re-distribution. Look for other examples such as EGSS (Stansted) EGKK (Gatwick) EGHH (Bournemouth - Hurn, hence the HH) etc etc. Latterly, TT is used for more recent additions (EGTP for Perranporth) and some military bases have EGDX (EGDR for RNAS Culdrose, EGDG for RAF St. Mawgan). When as part of the latter became Newquay Airport, they were assigned a Hurn daughter code, EGHQ (most aerodromes West of Bournemouth have a 'H' code, but there are anomalies, Bodmin is EGLA, how did that happen???)
The Unites States have a far simpler system. Each airport has an IATA (International Air Transport Association) 3-letter code, which you will see on your luggage label. The Americans simply add a 'K' to the IATA code to produce the ICAO code eg MCO (Orlando) becomes KMCO. Simple!
PS London Airport is on the A4 Bath Road and is otherwise known as Heath Row, 2 separate words (or LHR on your luggage tag) Beware if imitations!!! (London-Gatwick, London-Luton, London-Stansted, London - practically everywhere else in the South-East!!!)
TOO