Answers:
It can stand for a number of things:
EOA - Early Onset Alzheimer's
EOA - Early Operational Assessment
EOA - East of Adelaide (London, Ontario)
EOA - Eastern Orthopaedic Association
EOA - Effective On or About
EOA - Egyptian Orthopedic Association
EOA - Electrical Operating Area
EOA - Elevation-of-Arrival
EOA - Embassy of Aesthetics
EOA - Emerging Optical Access
EOA - End Of Address
EOA - End of Auction
EOA - End Of Availability
EOA - Entry of Appearance (courts)
EOA - Equal Opportunity Advisor
EOA - Esophageal Obturator Airway
EOA - Essential Oil Association (USA)
EOA - Ethics Officer Association
EOA - European Online Academy
EOA - Everquest Online Adventures (game)
EOA - Examination, Opinion, and Advice
EOA - Excess Ordering Authority (materials management)
EOA - Exercise Operating Area
The most common use seem to be End of Address and End of Auction.
Hope this helps,
Ken