This is knowledge that is generally “tribal” by nature, reserved to only the nerdiest web developers, recently I was asked to name these and failed. Here’s the bounty of my research.
Gecko is generally considered to be the second most-popular layout engine on the Web, after Trident (used by Internet Explorer for Windows since version 4), and followed by WebCore (used by Safari) and Presto (used by Opera).
Gecko is the open source, free software web browser layout engine used in all Mozilla-branded software and its derivatives, including later Netscape browser releases. Written in C++ and licensed under MPL/GPL/LGPL triple license, Gecko is designed to support open Internet standards. Originally created by Netscape Communications Corporation, its development is now overseen by the Mozilla Foundation.
Trident (also known as MSHTML) is the name of the layout engine for the Microsoft Windows version of Internet Explorer. It was first introduced with the release of Internet Explorer version 4 in October 1997, has been steadily upgraded and remains in use today. For version 7 of Internet Explorer, Microsoft made significant changes to the Trident layout engine to improve compliance with web standards and add support for new technologies. Despite these changes, Trident remains significantly less compliant than competing layout engines Gecko, Presto and WebCore.
Tasman is the name of the layout engine introduced with version 5 of Internet Explorer for Mac. Tasman was an attempt to improve support for web standards, as defined by the World Wide Web Consortium. At the time of its release, Tasman was seen as the layout engine with the best support for web standards such as HTML and CSS. Unfortunately, MSIE for Mac is no longer supported, but newer versions of Tasman are incorporated in some other current Microsoft products.