What does RDH stand for?

What does RDH mean?

RDH	Registered Dental Hygienist Business » Positions
RDH	Rabid Dogs of Hell Miscellaneous » Gaming
RDH	Recirculating Document Handler Business » Positions
RDH	Reference Datum Height Academic & Science » Geology
RDH	Rounthwaite, Dick and Hadley Architects Inc. Business » Firms
RDH	Royal Darwin Hospital Medical » Hospitals
RDH	Rapid Displacement Heating Academic & Science » Chemistry
RDH	Robin Da Hood Miscellaneous » Clothes
RDH	Redhill Education Limited Business » ASX Symbols